aboutsummaryrefslogtreecommitdiff
path: root/mesalib/src/mesa/main/framebuffer.c
blob: 6d5e4524a96f1fce28fc8c05a26fcde254c500a3 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
/*
 * Mesa 3-D graphics library
 * Version:  7.2
 *
 * Copyright (C) 1999-2008  Brian Paul   All Rights Reserved.
 *
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the "Software"),
 * to deal in the Software without restriction, including without limitation
 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
 * and/or sell copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included
 * in all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
 * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
 * BRIAN PAUL BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
 * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 */


/**
 * Functions for allocating/managing framebuffers and renderbuffers.
 * Also, routines for reading/writing renderbuffer data as ubytes,
 * ushorts, uints, etc.
 */


#include "glheader.h"
#include "imports.h"
#include "buffers.h"
#include "context.h"
#include "enums.h"
#include "formats.h"
#include "macros.h"
#include "mtypes.h"
#include "fbobject.h"
#include "framebuffer.h"
#include "renderbuffer.h"
#include "texobj.h"



/**
 * Compute/set the _DepthMax field for the given framebuffer.
 * This value depends on the Z buffer resolution.
 */
static void
compute_depth_max(struct gl_framebuffer *fb)
{
   if (fb->Visual.depthBits == 0) {
      /* Special case.  Even if we don't have a depth buffer we need
       * good values for DepthMax for Z vertex transformation purposes
       * and for per-fragment fog computation.
       */
      fb->_DepthMax = (1 << 16) - 1;
   }
   else if (fb->Visual.depthBits < 32) {
      fb->_DepthMax = (1 << fb->Visual.depthBits) - 1;
   }
   else {
      /* Special case since shift values greater than or equal to the
       * number of bits in the left hand expression's type are undefined.
       */
      fb->_DepthMax = 0xffffffff;
   }
   fb->_DepthMaxF = (GLfloat) fb->_DepthMax;

   /* Minimum resolvable depth value, for polygon offset */
   fb->_MRD = (GLfloat)1.0 / fb->_DepthMaxF;
}

/**
 * Create and initialize a gl_framebuffer object.
 * This is intended for creating _window_system_ framebuffers, not generic
 * framebuffer objects ala GL_EXT_framebuffer_object.
 *
 * \sa _mesa_new_framebuffer
 */
struct gl_framebuffer *
_mesa_create_framebuffer(const struct gl_config *visual)
{
   struct gl_framebuffer *fb = CALLOC_STRUCT(gl_framebuffer);
   assert(visual);
   if (fb) {
      _mesa_initialize_window_framebuffer(fb, visual);
   }
   return fb;
}


/**
 * Allocate a new gl_framebuffer object.
 * This is the default function for ctx->Driver.NewFramebuffer().
 * This is for allocating user-created framebuffers, not window-system
 * framebuffers!
 * \sa _mesa_create_framebuffer
 */
struct gl_framebuffer *
_mesa_new_framebuffer(struct gl_context *ctx, GLuint name)
{
   struct gl_framebuffer *fb;
   (void) ctx;
   assert(name != 0);
   fb = CALLOC_STRUCT(gl_framebuffer);
   if (fb) {
      _mesa_initialize_user_framebuffer(fb, name);
   }
   return fb;
}


/**
 * Initialize a gl_framebuffer object.  Typically used to initialize
 * window system-created framebuffers, not user-created framebuffers.
 * \sa _mesa_initialize_user_framebuffer
 */
void
_mesa_initialize_window_framebuffer(struct gl_framebuffer *fb,
				     const struct gl_config *visual)
{
   assert(fb);
   assert(visual);

   memset(fb, 0, sizeof(struct gl_framebuffer));

   _glthread_INIT_MUTEX(fb->Mutex);

   fb->RefCount = 1;

   /* save the visual */
   fb->Visual = *visual;

   /* Init read/draw renderbuffer state */
   if (visual->doubleBufferMode) {
      fb->_NumColorDrawBuffers = 1;
      fb->ColorDrawBuffer[0] = GL_BACK;
      fb->_ColorDrawBufferIndexes[0] = BUFFER_BACK_LEFT;
      fb->ColorReadBuffer = GL_BACK;
      fb->_ColorReadBufferIndex = BUFFER_BACK_LEFT;
   }
   else {
      fb->_NumColorDrawBuffers = 1;
      fb->ColorDrawBuffer[0] = GL_FRONT;
      fb->_ColorDrawBufferIndexes[0] = BUFFER_FRONT_LEFT;
      fb->ColorReadBuffer = GL_FRONT;
      fb->_ColorReadBufferIndex = BUFFER_FRONT_LEFT;
   }

   fb->Delete = _mesa_destroy_framebuffer;
   fb->_Status = GL_FRAMEBUFFER_COMPLETE_EXT;

   compute_depth_max(fb);
}


/**
 * Initialize a user-created gl_framebuffer object.
 * \sa _mesa_initialize_window_framebuffer
 */
void
_mesa_initialize_user_framebuffer(struct gl_framebuffer *fb, GLuint name)
{
   assert(fb);
   assert(name);

   memset(fb, 0, sizeof(struct gl_framebuffer));

   fb->Name = name;
   fb->RefCount = 1;
   fb->_NumColorDrawBuffers = 1;
   fb->ColorDrawBuffer[0] = GL_COLOR_ATTACHMENT0_EXT;
   fb->_ColorDrawBufferIndexes[0] = BUFFER_COLOR0;
   fb->ColorReadBuffer = GL_COLOR_ATTACHMENT0_EXT;
   fb->_ColorReadBufferIndex = BUFFER_COLOR0;
   fb->Delete = _mesa_destroy_framebuffer;
   _glthread_INIT_MUTEX(fb->Mutex);
}


/**
 * Deallocate buffer and everything attached to it.
 * Typically called via the gl_framebuffer->Delete() method.
 */
void
_mesa_destroy_framebuffer(struct gl_framebuffer *fb)
{
   if (fb) {
      _mesa_free_framebuffer_data(fb);
      free(fb);
   }
}


/**
 * Free all the data hanging off the given gl_framebuffer, but don't free
 * the gl_framebuffer object itself.
 */
void
_mesa_free_framebuffer_data(struct gl_framebuffer *fb)
{
   GLuint i;

   assert(fb);
   assert(fb->RefCount == 0);

   _glthread_DESTROY_MUTEX(fb->Mutex);

   for (i = 0; i < BUFFER_COUNT; i++) {
      struct gl_renderbuffer_attachment *att = &fb->Attachment[i];
      if (att->Renderbuffer) {
         _mesa_reference_renderbuffer(&att->Renderbuffer, NULL);
      }
      if (att->Texture) {
         _mesa_reference_texobj(&att->Texture, NULL);
      }
      ASSERT(!att->Renderbuffer);
      ASSERT(!att->Texture);
      att->Type = GL_NONE;
   }

   /* unbind _Depth/_StencilBuffer to decr ref counts */
   _mesa_reference_renderbuffer(&fb->_DepthBuffer, NULL);
   _mesa_reference_renderbuffer(&fb->_StencilBuffer, NULL);
}


/**
 * Set *ptr to point to fb, with refcounting and locking.
 * This is normally only called from the _mesa_reference_framebuffer() macro
 * when there's a real pointer change.
 */
void
_mesa_reference_framebuffer_(struct gl_framebuffer **ptr,
                             struct gl_framebuffer *fb)
{
   if (*ptr) {
      /* unreference old renderbuffer */
      GLboolean deleteFlag = GL_FALSE;
      struct gl_framebuffer *oldFb = *ptr;

      _glthread_LOCK_MUTEX(oldFb->Mutex);
      ASSERT(oldFb->RefCount > 0);
      oldFb->RefCount--;
      deleteFlag = (oldFb->RefCount == 0);
      _glthread_UNLOCK_MUTEX(oldFb->Mutex);
      
      if (deleteFlag)
         oldFb->Delete(oldFb);

      *ptr = NULL;
   }
   assert(!*ptr);

   if (fb) {
      _glthread_LOCK_MUTEX(fb->Mutex);
      fb->RefCount++;
      _glthread_UNLOCK_MUTEX(fb->Mutex);
      *ptr = fb;
   }
}


/**
 * Resize the given framebuffer's renderbuffers to the new width and height.
 * This should only be used for window-system framebuffers, not
 * user-created renderbuffers (i.e. made with GL_EXT_framebuffer_object).
 * This will typically be called via ctx->Driver.ResizeBuffers() or directly
 * from a device driver.
 *
 * \note it's possible for ctx to be null since a window can be resized
 * without a currently bound rendering context.
 */
void
_mesa_resize_framebuffer(struct gl_context *ctx, struct gl_framebuffer *fb,
                         GLuint width, GLuint height)
{
   GLuint i;

   /* XXX I think we could check if the size is not changing
    * and return early.
    */

   /* For window system framebuffers, Name is zero */
   assert(fb->Name == 0);

   for (i = 0; i < BUFFER_COUNT; i++) {
      struct gl_renderbuffer_attachment *att = &fb->Attachment[i];
      if (att->Type == GL_RENDERBUFFER_EXT && att->Renderbuffer) {
         struct gl_renderbuffer *rb = att->Renderbuffer;
         /* only resize if size is changing */
         if (rb->Width != width || rb->Height != height) {
            if (rb->AllocStorage(ctx, rb, rb->InternalFormat, width, height)) {
               ASSERT(rb->Width == width);
               ASSERT(rb->Height == height);
            }
            else {
               _mesa_error(ctx, GL_OUT_OF_MEMORY, "Resizing framebuffer");
               /* no return */
            }
         }
      }
   }

   fb->Width = width;
   fb->Height = height;

   if (ctx) {
      /* update scissor / window bounds */
      _mesa_update_draw_buffer_bounds(ctx);
      /* Signal new buffer state so that swrast will update its clipping
       * info (the CLIP_BIT flag).
       */
      ctx->NewState |= _NEW_BUFFERS;
   }
}



/**
 * XXX THIS IS OBSOLETE - drivers should take care of detecting window
 * size changes and act accordingly, likely calling _mesa_resize_framebuffer().
 *
 * GL_MESA_resize_buffers extension.
 *
 * When this function is called, we'll ask the window system how large
 * the current window is.  If it's a new size, we'll call the driver's
 * ResizeBuffers function.  The driver will then resize its color buffers
 * as needed, and maybe call the swrast's routine for reallocating
 * swrast-managed depth/stencil/accum/etc buffers.
 * \note This function should only be called through the GL API, not
 * from device drivers (as was done in the past).
 */
void
_mesa_resizebuffers( struct gl_context *ctx )
{
   ASSERT_OUTSIDE_BEGIN_END_AND_FLUSH( ctx );

   if (MESA_VERBOSE & VERBOSE_API)
      _mesa_debug(ctx, "glResizeBuffersMESA\n");

   if (!ctx->Driver.GetBufferSize) {
      return;
   }

   if (ctx->WinSysDrawBuffer) {
      GLuint newWidth, newHeight;
      struct gl_framebuffer *buffer = ctx->WinSysDrawBuffer;

      assert(buffer->Name == 0);

      /* ask device driver for size of output buffer */
      ctx->Driver.GetBufferSize( buffer, &newWidth, &newHeight );

      /* see if size of device driver's color buffer (window) has changed */
      if (buffer->Width != newWidth || buffer->Height != newHeight) {
         if (ctx->Driver.ResizeBuffers)
            ctx->Driver.ResizeBuffers(ctx, buffer, newWidth, newHeight );
      }
   }

   if (ctx->WinSysReadBuffer
       && ctx->WinSysReadBuffer != ctx->WinSysDrawBuffer) {
      GLuint newWidth, newHeight;
      struct gl_framebuffer *buffer = ctx->WinSysReadBuffer;

      assert(buffer->Name == 0);

      /* ask device driver for size of read buffer */
      ctx->Driver.GetBufferSize( buffer, &newWidth, &newHeight );

      /* see if size of device driver's color buffer (window) has changed */
      if (buffer->Width != newWidth || buffer->Height != newHeight) {
         if (ctx->Driver.ResizeBuffers)
            ctx->Driver.ResizeBuffers(ctx, buffer, newWidth, newHeight );
      }
   }

   ctx->NewState |= _NEW_BUFFERS;  /* to update scissor / window bounds */
}


/*
 * XXX THIS IS OBSOLETE
 */
void GLAPIENTRY
_mesa_ResizeBuffersMESA( void )
{
   GET_CURRENT_CONTEXT(ctx);

   if (ctx->Extensions.MESA_resize_buffers)
      _mesa_resizebuffers( ctx );
}



/**
 * Examine all the framebuffer's renderbuffers to update the Width/Height
 * fields of the framebuffer.  If we have renderbuffers with different
 * sizes, set the framebuffer's width and height to the min size.
 * Note: this is only intended for user-created framebuffers, not
 * window-system framebuffes.
 */
static void
update_framebuffer_size(struct gl_context *ctx, struct gl_framebuffer *fb)
{
   GLuint minWidth = ~0, minHeight = ~0;
   GLuint i;

   /* user-created framebuffers only */
   assert(fb->Name);

   for (i = 0; i < BUFFER_COUNT; i++) {
      struct gl_renderbuffer_attachment *att = &fb->Attachment[i];
      const struct gl_renderbuffer *rb = att->Renderbuffer;
      if (rb) {
         minWidth = MIN2(minWidth, rb->Width);
         minHeight = MIN2(minHeight, rb->Height);
      }
   }

   if (minWidth != ~0) {
      fb->Width = minWidth;
      fb->Height = minHeight;
   }
   else {
      fb->Width = 0;
      fb->Height = 0;
   }
}


/**
 * Update the context's current drawing buffer's Xmin, Xmax, Ymin, Ymax fields.
 * These values are computed from the buffer's width and height and
 * the scissor box, if it's enabled.
 * \param ctx  the GL context.
 */
void
_mesa_update_draw_buffer_bounds(struct gl_context *ctx)
{
   struct gl_framebuffer *buffer = ctx->DrawBuffer;

   if (!buffer)
      return;

   if (buffer->Name) {
      /* user-created framebuffer size depends on the renderbuffers */
      update_framebuffer_size(ctx, buffer);
   }

   buffer->_Xmin = 0;
   buffer->_Ymin = 0;
   buffer->_Xmax = buffer->Width;
   buffer->_Ymax = buffer->Height;

   if (ctx->Scissor.Enabled) {
      if (ctx->Scissor.X > buffer->_Xmin) {
	 buffer->_Xmin = ctx->Scissor.X;
      }
      if (ctx->Scissor.Y > buffer->_Ymin) {
	 buffer->_Ymin = ctx->Scissor.Y;
      }
      if (ctx->Scissor.X + ctx->Scissor.Width < buffer->_Xmax) {
	 buffer->_Xmax = ctx->Scissor.X + ctx->Scissor.Width;
      }
      if (ctx->Scissor.Y + ctx->Scissor.Height < buffer->_Ymax) {
	 buffer->_Ymax = ctx->Scissor.Y + ctx->Scissor.Height;
      }
      /* finally, check for empty region */
      if (buffer->_Xmin > buffer->_Xmax) {
         buffer->_Xmin = buffer->_Xmax;
      }
      if (buffer->_Ymin > buffer->_Ymax) {
         buffer->_Ymin = buffer->_Ymax;
      }
   }

   ASSERT(buffer->_Xmin <= buffer->_Xmax);
   ASSERT(buffer->_Ymin <= buffer->_Ymax);
}


/**
 * The glGet queries of the framebuffer red/green/blue size, stencil size,
 * etc. are satisfied by the fields of ctx->DrawBuffer->Visual.  These can
 * change depending on the renderbuffer bindings.  This function updates
 * the given framebuffer's Visual from the current renderbuffer bindings.
 *
 * This may apply to user-created framebuffers or window system framebuffers.
 *
 * Also note: ctx->DrawBuffer->Visual.depthBits might not equal
 * ctx->DrawBuffer->Attachment[BUFFER_DEPTH].Renderbuffer.DepthBits.
 * The former one is used to convert floating point depth values into
 * integer Z values.
 */
void
_mesa_update_framebuffer_visual(struct gl_context *ctx,
				struct gl_framebuffer *fb)
{
   GLuint i;

   memset(&fb->Visual, 0, sizeof(fb->Visual));
   fb->Visual.rgbMode = GL_TRUE; /* assume this */

#if 0 /* this _might_ be needed */
   if (fb->_Status != GL_FRAMEBUFFER_COMPLETE_EXT) {
      /* leave visual fields zero'd */
      return;
   }
#endif

   /* find first RGB renderbuffer */
   for (i = 0; i < BUFFER_COUNT; i++) {
      if (fb->Attachment[i].Renderbuffer) {
         const struct gl_renderbuffer *rb = fb->Attachment[i].Renderbuffer;
         const GLenum baseFormat = _mesa_get_format_base_format(rb->Format);
         const gl_format fmt = rb->Format;

         if (_mesa_is_legal_color_format(ctx, baseFormat)) {
            fb->Visual.redBits = _mesa_get_format_bits(fmt, GL_RED_BITS);
            fb->Visual.greenBits = _mesa_get_format_bits(fmt, GL_GREEN_BITS);
            fb->Visual.blueBits = _mesa_get_format_bits(fmt, GL_BLUE_BITS);
            fb->Visual.alphaBits = _mesa_get_format_bits(fmt, GL_ALPHA_BITS);
            fb->Visual.rgbBits = fb->Visual.redBits
               + fb->Visual.greenBits + fb->Visual.blueBits;
            fb->Visual.samples = rb->NumSamples;
            fb->Visual.sampleBuffers = rb->NumSamples > 0 ? 1 : 0;
            if (_mesa_get_format_color_encoding(fmt) == GL_SRGB)
                fb->Visual.sRGBCapable = ctx->Const.sRGBCapable;
            break;
         }
      }
   }

   fb->Visual.floatMode = GL_FALSE;
   for (i = 0; i < BUFFER_COUNT; i++) {
      if (fb->Attachment[i].Renderbuffer) {
         const struct gl_renderbuffer *rb = fb->Attachment[i].Renderbuffer;
         const gl_format fmt = rb->Format;

         if (_mesa_get_format_datatype(fmt) == GL_FLOAT) {
            fb->Visual.floatMode = GL_TRUE;
            break;
         }
      }
   }

   if (fb->Attachment[BUFFER_DEPTH].Renderbuffer) {
      const struct gl_renderbuffer *rb =
         fb->Attachment[BUFFER_DEPTH].Renderbuffer;
      const gl_format fmt = rb->Format;
      fb->Visual.haveDepthBuffer = GL_TRUE;
      fb->Visual.depthBits = _mesa_get_format_bits(fmt, GL_DEPTH_BITS);
   }

   if (fb->Attachment[BUFFER_STENCIL].Renderbuffer) {
      const struct gl_renderbuffer *rb =
         fb->Attachment[BUFFER_STENCIL].Renderbuffer;
      const gl_format fmt = rb->Format;
      fb->Visual.haveStencilBuffer = GL_TRUE;
      fb->Visual.stencilBits = _mesa_get_format_bits(fmt, GL_STENCIL_BITS);
   }

   if (fb->Attachment[BUFFER_ACCUM].Renderbuffer) {
      const struct gl_renderbuffer *rb =
         fb->Attachment[BUFFER_ACCUM].Renderbuffer;
      const gl_format fmt = rb->Format;
      fb->Visual.haveAccumBuffer = GL_TRUE;
      fb->Visual.accumRedBits = _mesa_get_format_bits(fmt, GL_RED_BITS);
      fb->Visual.accumGreenBits = _mesa_get_format_bits(fmt, GL_GREEN_BITS);
      fb->Visual.accumBlueBits = _mesa_get_format_bits(fmt, GL_BLUE_BITS);
      fb->Visual.accumAlphaBits = _mesa_get_format_bits(fmt, GL_ALPHA_BITS);
   }

   compute_depth_max(fb);
}


/*
 * Example DrawBuffers scenarios:
 *
 * 1. glDrawBuffer(GL_FRONT_AND_BACK), fixed-func or shader writes to
 * "gl_FragColor" or program writes to the "result.color" register:
 *
 *   fragment color output   renderbuffer
 *   ---------------------   ---------------
 *   color[0]                Front, Back
 *
 *
 * 2. glDrawBuffers(3, [GL_FRONT, GL_AUX0, GL_AUX1]), shader writes to
 * gl_FragData[i] or program writes to result.color[i] registers:
 *
 *   fragment color output   renderbuffer
 *   ---------------------   ---------------
 *   color[0]                Front
 *   color[1]                Aux0
 *   color[3]                Aux1
 *
 *
 * 3. glDrawBuffers(3, [GL_FRONT, GL_AUX0, GL_AUX1]) and shader writes to
 * gl_FragColor, or fixed function:
 *
 *   fragment color output   renderbuffer
 *   ---------------------   ---------------
 *   color[0]                Front, Aux0, Aux1
 *
 *
 * In either case, the list of renderbuffers is stored in the
 * framebuffer->_ColorDrawBuffers[] array and
 * framebuffer->_NumColorDrawBuffers indicates the number of buffers.
 * The renderer (like swrast) has to look at the current fragment shader
 * to see if it writes to gl_FragColor vs. gl_FragData[i] to determine
 * how to map color outputs to renderbuffers.
 *
 * Note that these two calls are equivalent (for fixed function fragment
 * shading anyway):
 *   a)  glDrawBuffer(GL_FRONT_AND_BACK);  (assuming non-stereo framebuffer)
 *   b)  glDrawBuffers(2, [GL_FRONT_LEFT, GL_BACK_LEFT]);
 */




/**
 * Update the (derived) list of color drawing renderbuffer pointers.
 * Later, when we're rendering we'll loop from 0 to _NumColorDrawBuffers
 * writing colors.
 */
static void
update_color_draw_buffers(struct gl_context *ctx, struct gl_framebuffer *fb)
{
   GLuint output;

   /* set 0th buffer to NULL now in case _NumColorDrawBuffers is zero */
   fb->_ColorDrawBuffers[0] = NULL;

   for (output = 0; output < fb->_NumColorDrawBuffers; output++) {
      GLint buf = fb->_ColorDrawBufferIndexes[output];
      if (buf >= 0) {
         fb->_ColorDrawBuffers[output] = fb->Attachment[buf].Renderbuffer;
      }
      else {
         fb->_ColorDrawBuffers[output] = NULL;
      }
   }
}


/**
 * Update the (derived) color read renderbuffer pointer.
 * Unlike the DrawBuffer, we can only read from one (or zero) color buffers.
 */
static void
update_color_read_buffer(struct gl_context *ctx, struct gl_framebuffer *fb)
{
   (void) ctx;
   if (fb->_ColorReadBufferIndex == -1 ||
       fb->DeletePending ||
       fb->Width == 0 ||
       fb->Height == 0) {
      fb->_ColorReadBuffer = NULL; /* legal! */
   }
   else {
      ASSERT(fb->_ColorReadBufferIndex >= 0);
      ASSERT(fb->_ColorReadBufferIndex < BUFFER_COUNT);
      fb->_ColorReadBuffer
         = fb->Attachment[fb->_ColorReadBufferIndex].Renderbuffer;
   }
}


/**
 * Update a gl_framebuffer's derived state.
 *
 * Specifically, update these framebuffer fields:
 *    _ColorDrawBuffers
 *    _NumColorDrawBuffers
 *    _ColorReadBuffer
 *    _DepthBuffer
 *    _StencilBuffer
 *
 * If the framebuffer is user-created, make sure it's complete.
 *
 * The following functions (at least) can effect framebuffer state:
 * glReadBuffer, glDrawBuffer, glDrawBuffersARB, glFramebufferRenderbufferEXT,
 * glRenderbufferStorageEXT.
 */
static void
update_framebuffer(struct gl_context *ctx, struct gl_framebuffer *fb)
{
   if (fb->Name == 0) {
      /* This is a window-system framebuffer */
      /* Need to update the FB's GL_DRAW_BUFFER state to match the
       * context state (GL_READ_BUFFER too).
       */
      if (fb->ColorDrawBuffer[0] != ctx->Color.DrawBuffer[0]) {
         _mesa_drawbuffers(ctx, ctx->Const.MaxDrawBuffers,
                           ctx->Color.DrawBuffer, NULL);
      }
   }
   else {
      /* This is a user-created framebuffer.
       * Completeness only matters for user-created framebuffers.
       */
      if (fb->_Status != GL_FRAMEBUFFER_COMPLETE) {
         _mesa_test_framebuffer_completeness(ctx, fb);
      }
   }

   /* Strictly speaking, we don't need to update the draw-state
    * if this FB is bound as ctx->ReadBuffer (and conversely, the
    * read-state if this FB is bound as ctx->DrawBuffer), but no
    * harm.
    */
   update_color_draw_buffers(ctx, fb);
   update_color_read_buffer(ctx, fb);

   compute_depth_max(fb);
}


/**
 * Update state related to the current draw/read framebuffers.
 */
void
_mesa_update_framebuffer(struct gl_context *ctx)
{
   struct gl_framebuffer *drawFb;
   struct gl_framebuffer *readFb;

   assert(ctx);
   drawFb = ctx->DrawBuffer;
   readFb = ctx->ReadBuffer;

   update_framebuffer(ctx, drawFb);
   if (readFb != drawFb)
      update_framebuffer(ctx, readFb);
}


/**
 * Check if the renderbuffer for a read/draw operation exists.
 * \param format  a basic image format such as GL_RGB, GL_RGBA, GL_ALPHA,
 *                GL_DEPTH_COMPONENT, etc. or GL_COLOR, GL_DEPTH, GL_STENCIL.
 * \param reading  if TRUE, we're going to read from the buffer,
                   if FALSE, we're going to write to the buffer.
 * \return GL_TRUE if buffer exists, GL_FALSE otherwise
 */
static GLboolean
renderbuffer_exists(struct gl_context *ctx,
                    struct gl_framebuffer *fb,
                    GLenum format,
                    GLboolean reading)
{
   const struct gl_renderbuffer_attachment *att = fb->Attachment;

   /* If we don't know the framebuffer status, update it now */
   if (fb->_Status == 0) {
      _mesa_test_framebuffer_completeness(ctx, fb);
   }

   if (fb->_Status != GL_FRAMEBUFFER_COMPLETE_EXT) {
      return GL_FALSE;
   }

   switch (format) {
   case GL_COLOR:
   case GL_RED:
   case GL_GREEN:
   case GL_BLUE:
   case GL_ALPHA:
   case GL_LUMINANCE:
   case GL_LUMINANCE_ALPHA:
   case GL_INTENSITY:
   case GL_RG:
   case GL_RGB:
   case GL_BGR:
   case GL_RGBA:
   case GL_BGRA:
   case GL_ABGR_EXT:
   case GL_RED_INTEGER_EXT:
   case GL_RG_INTEGER:
   case GL_GREEN_INTEGER_EXT:
   case GL_BLUE_INTEGER_EXT:
   case GL_ALPHA_INTEGER_EXT:
   case GL_RGB_INTEGER_EXT:
   case GL_RGBA_INTEGER_EXT:
   case GL_BGR_INTEGER_EXT:
   case GL_BGRA_INTEGER_EXT:
   case GL_LUMINANCE_INTEGER_EXT:
   case GL_LUMINANCE_ALPHA_INTEGER_EXT:
      if (reading) {
         /* about to read from a color buffer */
         const struct gl_renderbuffer *readBuf = fb->_ColorReadBuffer;
         if (!readBuf) {
            return GL_FALSE;
         }
         ASSERT(_mesa_get_format_bits(readBuf->Format, GL_RED_BITS) > 0 ||
                _mesa_get_format_bits(readBuf->Format, GL_ALPHA_BITS) > 0 ||
                _mesa_get_format_bits(readBuf->Format, GL_TEXTURE_LUMINANCE_SIZE) > 0 ||
                _mesa_get_format_bits(readBuf->Format, GL_TEXTURE_INTENSITY_SIZE) > 0 ||
                _mesa_get_format_bits(readBuf->Format, GL_INDEX_BITS) > 0);
      }
      else {
         /* about to draw to zero or more color buffers (none is OK) */
         return GL_TRUE;
      }
      break;
   case GL_DEPTH:
   case GL_DEPTH_COMPONENT:
      if (att[BUFFER_DEPTH].Type == GL_NONE) {
         return GL_FALSE;
      }
      break;
   case GL_STENCIL:
   case GL_STENCIL_INDEX:
      if (att[BUFFER_STENCIL].Type == GL_NONE) {
         return GL_FALSE;
      }
      break;
   case GL_DEPTH_STENCIL_EXT:
      if (att[BUFFER_DEPTH].Type == GL_NONE ||
          att[BUFFER_STENCIL].Type == GL_NONE) {
         return GL_FALSE;
      }
      break;
   default:
      _mesa_problem(ctx,
                    "Unexpected format 0x%x in renderbuffer_exists",
                    format);
      return GL_FALSE;
   }

   /* OK */
   return GL_TRUE;
}


/**
 * Check if the renderbuffer for a read operation (glReadPixels, glCopyPixels,
 * glCopyTex[Sub]Image, etc) exists.
 * \param format  a basic image format such as GL_RGB, GL_RGBA, GL_ALPHA,
 *                GL_DEPTH_COMPONENT, etc. or GL_COLOR, GL_DEPTH, GL_STENCIL.
 * \return GL_TRUE if buffer exists, GL_FALSE otherwise
 */
GLboolean
_mesa_source_buffer_exists(struct gl_context *ctx, GLenum format)
{
   return renderbuffer_exists(ctx, ctx->ReadBuffer, format, GL_TRUE);
}


/**
 * As above, but for drawing operations.
 * XXX could do some code merging w/ above function.
 */
GLboolean
_mesa_dest_buffer_exists(struct gl_context *ctx, GLenum format)
{
   return renderbuffer_exists(ctx, ctx->DrawBuffer, format, GL_FALSE);
}


/**
 * Used to answer the GL_IMPLEMENTATION_COLOR_READ_FORMAT_OES query.
 */
GLenum
_mesa_get_color_read_format(struct gl_context *ctx)
{
   switch (ctx->ReadBuffer->_ColorReadBuffer->Format) {
   case MESA_FORMAT_ARGB8888:
      return GL_BGRA;
   case MESA_FORMAT_RGB565:
      return GL_BGR;
   default:
      return GL_RGBA;
   }
}


/**
 * Used to answer the GL_IMPLEMENTATION_COLOR_READ_TYPE_OES query.
 */
GLenum
_mesa_get_color_read_type(struct gl_context *ctx)
{
   switch (ctx->ReadBuffer->_ColorReadBuffer->Format) {
   case MESA_FORMAT_ARGB8888:
      return GL_UNSIGNED_BYTE;
   case MESA_FORMAT_RGB565:
      return GL_UNSIGNED_SHORT_5_6_5_REV;
   default:
      return GL_UNSIGNED_BYTE;
   }
}


/**
 * Print framebuffer info to stderr, for debugging.
 */
void
_mesa_print_framebuffer(const struct gl_framebuffer *fb)
{
   GLuint i;

   fprintf(stderr, "Mesa Framebuffer %u at %p\n", fb->Name, (void *) fb);
   fprintf(stderr, "  Size: %u x %u  Status: %s\n", fb->Width, fb->Height,
           _mesa_lookup_enum_by_nr(fb->_Status));
   fprintf(stderr, "  Attachments:\n");

   for (i = 0; i < BUFFER_COUNT; i++) {
      const struct gl_renderbuffer_attachment *att = &fb->Attachment[i];
      if (att->Type == GL_TEXTURE) {
         const struct gl_texture_image *texImage =
            _mesa_get_attachment_teximage_const(att);
         fprintf(stderr,
                 "  %2d: Texture %u, level %u, face %u, slice %u, complete %d\n",
                 i, att->Texture->Name, att->TextureLevel, att->CubeMapFace,
                 att->Zoffset, att->Complete);
         fprintf(stderr, "       Size: %u x %u x %u  Format %s\n",
                 texImage->Width, texImage->Height, texImage->Depth,
                 _mesa_get_format_name(texImage->TexFormat));
      }
      else if (att->Type == GL_RENDERBUFFER) {
         fprintf(stderr, "  %2d: Renderbuffer %u, complete %d\n",
                 i, att->Renderbuffer->Name, att->Complete);
         fprintf(stderr, "       Size: %u x %u  Format %s\n",
                 att->Renderbuffer->Width, att->Renderbuffer->Height,
                 _mesa_get_format_name(att->Renderbuffer->Format));
      }
      else {
         fprintf(stderr, "  %2d: none\n", i);
      }
   }
}